// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2010, 2013 Jitse Niesen <jitse@maths.leeds.ac.uk>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_STEM_FUNCTION
#define EIGEN_STEM_FUNCTION

namespace Eigen {

namespace internal {

    /** \brief The exponential function (and its derivatives). */
    template <typename Scalar> Scalar stem_function_exp(Scalar x, int)
    {
        using std::exp;
        return exp(x);
    }

    /** \brief Cosine (and its derivatives). */
    template <typename Scalar> Scalar stem_function_cos(Scalar x, int n)
    {
        using std::cos;
        using std::sin;
        Scalar res;

        switch (n % 4)
        {
        case 0:
            res = std::cos(x);
            break;
        case 1:
            res = -std::sin(x);
            break;
        case 2:
            res = -std::cos(x);
            break;
        case 3:
            res = std::sin(x);
            break;
        }
        return res;
    }

    /** \brief Sine (and its derivatives). */
    template <typename Scalar> Scalar stem_function_sin(Scalar x, int n)
    {
        using std::cos;
        using std::sin;
        Scalar res;

        switch (n % 4)
        {
        case 0:
            res = std::sin(x);
            break;
        case 1:
            res = std::cos(x);
            break;
        case 2:
            res = -std::sin(x);
            break;
        case 3:
            res = -std::cos(x);
            break;
        }
        return res;
    }

    /** \brief Hyperbolic cosine (and its derivatives). */
    template <typename Scalar> Scalar stem_function_cosh(Scalar x, int n)
    {
        using std::cosh;
        using std::sinh;
        Scalar res;

        switch (n % 2)
        {
        case 0:
            res = std::cosh(x);
            break;
        case 1:
            res = std::sinh(x);
            break;
        }
        return res;
    }

    /** \brief Hyperbolic sine (and its derivatives). */
    template <typename Scalar> Scalar stem_function_sinh(Scalar x, int n)
    {
        using std::cosh;
        using std::sinh;
        Scalar res;

        switch (n % 2)
        {
        case 0:
            res = std::sinh(x);
            break;
        case 1:
            res = std::cosh(x);
            break;
        }
        return res;
    }

}  // end namespace internal

}  // end namespace Eigen

#endif  // EIGEN_STEM_FUNCTION
